This invention relates to a burner assembly and, more particularly, to an improved burner assembly which operates in a manner to reduce the formation of nitric oxides as a result of fuel combustion.
A great deal of attention has recently been directed to the reduction of nitric oxides resulting from the combustion of fuel, and especially in connection with the furnace sections of relatively large installations such as vapor generators and the like.
In these type of arrangements, one or more burners are usually disposed in communication with the interior of the furnace and operate to combust pulverized solid fuel in air. The burners used in these arrangements are generally the type in which a swirling fuel-air mixture is continuously injected through a single nozzle so as to form a relatively large and single flame. As a result, the surface area of the flame is relatively small as compared to its volume and therefore the average flame temperature is relatively high. This condition, in turn, leads to the production of high levels of nitrogen oxides in the final combustion products which cause severe air pollution problems.
Although several attempts have been made to suppress the formation of nitric oxides, including techniques involving two stage combustion and flue gas recirculation, they often result in added expense in terms of contruction costs, etc., and lead to other related problems, such as the production of soot.